This invention relates to a spring pad for elastically supporting a felt cover. The felt cover is rolled on the periphery of a rotatable drum of a sheet ironing machine which is used to press and finish a flat sheet of material, such as a bed sheet, table cloth and so on.
The item to be ironed, using the sheet ironing machine, is finished by putting the item between a roller or drum and a bed which is heated by steam or a thermal medium of oil. The finishing procedure results in the drying, pressing and ironing, whilst the residual water contained in the washed item becomes vapour due to the heated bed. The vapour is discharged from the side of the roller.
On the periphery of the rotatable drum is rolled a spring pad, on the outer periphery of which is positioned a felt cover.
Conventionally, there is known a spring pad as disclosed in patent application EP0736627A1 by the same applicant as the present application. The said spring pad has a plurality of coil springs arranged in predetermined spaced relationship along the longitudinal extent of the upper side of a backing strip. The backing strip contacts the periphery of the roller of the sheet ironing machine. Said coil spring has a top plate at its centre transverse portion. Said top plate is made from a press machined stainless steel band. The said top plate is made by stamping an elongate strip material to leave adjacent plates connected to one another by frangible sections which are cut by pressing works.
With the conventional spring pad for a sheet ironing machine, however, the space between adjacent top plates becomes larger when the backing strip of the spring pad is rolled on the periphery of the roller, because the top plates are mounted slightly spaced from each other on each coil spring. The space between adjacent top plates causes a scar or unsightly wrinkle on the surface of the felt cover, which contacts each top plate. This causes poor ironing finishing, such as folds, wrinkles and so on.
To avoid such marks caused by the spacing of the top plates, a thicker felt cover is needed. The felt cover employs expensive heat resistant aramid fibre, and thus the thicker felt cover increases the manufacturing cost of the sheet ironing machine, as well as decreasing the ventilation effect. The decreased ventilation decreases a drying effect (in other words, increases drying time) and impacts the finished quality of the item being ironed.